Web humidifying method



March 5, 1963 H. P. FRY, JR 3,079,699

WEB HUMIDIFYINC METHOD Filed Oct. 27, less 3,979,699 WEB HUMIDEFYWGMETHQE) Horace P. Fry, .in, West (Ihester, Pa, assigns: to AmericanViscose Corporation, Philadelphia, Pa, a corporation of Delaware FiledGet. 27, 1958, Ser. No. 79,752 2 Claims. (Cl. 34-43) The presentinvention relates to the application of moisture to sheet materials, andmore particularly to a method for humidifying a traveling web of sheetmaterial.

During the manufacture, storage, conversion and use, sheet materials, asfor example paper, films, fabrics, etc., undergo a considerable loss ofmoisture. With conventional and known procedures, restoration or"moisture into the sheet material is achieved by exposing the same tohumid air under atmospheric pressure and at an elevated temperature ofabout 212 F. or below. Increasing the pressure on the humidifying air isnot generally possible with existing equipment, while elevating thetemperature of the moist air tends to superheat the same and introducesa condition wherein the moisture is actually extracted from the sheetmaterial. Accordingly, the primary object of this invention is toprovide an improved method for restoring moisture to traveling sheetmaterials.

Another object is the provision of the method for humidifying sheetmaterials uniformly and at a greater speed than heretofore possible.

Still another object is to provide an improved humidifying methodwherein a sheet material is subjected to vaporized moisture which isunder a pressure greater than atmospheric pressure.

A further object is the provision of a humidifying method whereinmoisture is heated while being confined against a sheet material wherebythe moisture is transformed into a. vaporous condition and migrates intothe sheet material under increased pressure as it expands.

These and other objects and advantages of the invention will be apparentfrom the following description and accompanying drawing in which:

FIGURE 1 is a shortened vertical section taken longitudinally of theapparatus employed in the method of the present invention;

FIGURE 2 is a vertical section taken longitudinally through a portion ofa roll employed in the apparatus shown in FIGURE 1;

FIGURE 3 is an end view of a single roll illustrating a modifiedarrangement for applying the moisture to a sheet material;

FIGURE 4 is a view similar to FIGURE 3 means for applying moisture to aroll surface;

FIGURE. 5 is a view similar to FIGURE 4 illustrating a modified rollconstruction; and

FIGURE 6 is an end view of a roll having a porous peripheral surfacewhich is capable of passing a humidifying atmosphere.

In general, application or restoration of moisture to sheet materials inaccordance with the present invention is achieved by trapping orconfining moisture between the sheet material and a heated surface,whereby its vaporization and accompanying expansion causes the same tomigrate into the sheet material under a pressure greater thanatmospheric pressure. Following this humidifying treatment the sheetmaterial is cooled to condense the moisture contained therein.

With reference to FlGURE l of the drawing, the sheet material to behumidified, such as illustrated at 15, is passed over and is advancedwith a series of spaced rolls 17 which are maintained in a heatedcondition so as to showing EQQ vaporize moisture applied to the sheetmaterial, as by nozzles 19. Pairs of guide rolls 21 and 23 maintain thesheet material 15 engaged with substantial portions of the peripheriesof the rolls 17 and, in addition, cooperate with the rolls 17 to preventthe escape of moisture as it expands during its transformation into avaporous state. The rolls 17 are driven as indicated by arrows in FIG-URE 1 by any suitable means, not shown, and the sheet material 15 ismaintained under sufficient tension so as to msure that its longitudinaledges are pressed snugly against the roll surfaces. From the structureand procedure thus far described, it will be apparent that the moistureis effectively trapped or sealed against escape while the sheet materialtravels with the rolls 17 and will therefore migrate into the sheetmaterial under increased pressure as it expands during its vaporization.

As the sheet material 15 leaves the last of the series of rolls 17, itis passed about a guide roll 25 and over a chill roll 27 w ere it iscooled to condense the moisture carried therein. To contain the hothumid atmosphere which is evolved during the humidifying procedure, theseries of rolls 17 are enclosed within a housing or chamber 29 havingelongated slots 31 and 33 in its opposite end walls to permit thecontinuous passage of the sheet material 15.

The rolls 17 are of known construction, each being provided withconcentric hollow shafts 35 and 37 through which a heated fluid, as forexample hot water, is circulated to maintain the rolls at a desiredelevated temperature. In a similar fashion, the chill roll 27 is alsoformed with concentric hollow shafts 39 an 41 through which cool wateror chilled brine is circulated. It will of course be understood thatother heating and chilling surfaces, such as endless metallic belts, maybe substituted for the rolls described above, and that electricalheating and air cooling may be employed in lieu of circulating fluids.

if desired, the longitudinal edges of the sheet material 15 may be moresnugly held against the surfaces of the rolls 17 by means of pairs ofcooperating endless belts 43 which, as shown in FIGURE 1, are trainedover a series of rolls or pulleys 45, at least one of which is driven bysuitable means, not shown. The endless belts 43 are not intended toadvance the sheet material 15 but serve primarily as a means for sealingthe longitudinal edges of the sheet material to prevent the escape ofmoisture during its expansion. The use of endl ss sealing belts 43, ofcourse, reduces or eliminates any tendency for the sheet material 15 totear or stretch, as when the sheet material is subjected to unduetension, and is of special importance when fragile sheet materials arebeing treated.

To achieve a greater degree of humidification and/or to increase therate of humidification without a corresponding increase in the size ofthe structure, the sheet material may be chilled after leaving selectedor each of the rolls 17, thus subjecting the sheet material to alternateheating and cooling stages. This cooling of the sheet material may beaccomplished by a dip roll 4-7 which applies cool water from a tank 49,or alternatively an internally cooled chill roll, similar to the chillroll 27, may be employed. It will be understood that chilling the sheetmaterial 15 during its passage through the chamber ER is not essentialto the satisfactory practics of the present invention, and thereforeonly a final cooling of the sheet material, as by the chill roll 27,need be employed.

In lieu of applying a mist of moisture to the sheet material and theperipheries of the rolls 17, as is accomished by the nozzles 19,moisture may be applied to the sheet material in a manner as shown inFIGURE 3 wherein a dip roller 51, turned by the advancing sheetmaterial, delivers water from a tank 53 to the sheet material as ittravels over the guide roll 21. A further modification is illustrated inFIGURE 4- wherein liquid from a tank 55 is applied directly to theperiphery of a roll 17 by a dip roller 57 which engages and turnstherewith. The structure illustrated in FIGURE is generally similar tothat shown in FIGURE 4 with the exception that the roll 17 is providedwith an outer absorbent covering 59, as for example of felt. Oneparticular advantage of this last-mentioned arrangement is that theabsorbent covering 59 quickly absorbs the moisture applied by the diproller 57 and thus there is no tendency for any moisture to be squeezedfrom the sheet material as it travels between the roll 17 and the guideroll 21.

The'roll structure 61 shown in FIGURE 6 difiers from the heated rollsdescribed above in that the roll61 is provided with a porous peripheralsurface 63 formed, for example, by a mass of powdered metal particlessintered or otherwise bonded into an integral cylindrical unit. Withthis'arrangement, the liquid to be vaporized may be applied to eitherthe sheet material 15, as shown in FIGURES 1' and '3, or to the rollperiphery, as shown in FIGURE 4, whilera heated medium, as for exampleair, is delivered through a hollow shaft 65 andlpasses through theporous roll periphery. It is preferred, however, 'to apply the moistureto the sheet material in a heated'condition directly throughtheporous'wall 63 of the roll, as for example in'the form of wet'steamunder pressure. This procedure insures that the applied moisture has noopportunity to escape" before it is further vaporized as the sheetmaterial'lS travels with the heated wall of the roll 61. I

The degree of sheet material humidification isof course controlled byregulating the number of heated rolls employed, the temperature of theheating and cooling surfaces or mediums, and the rate of advancement ofthe sheet'material, and thus the procedure described can be modified tobest suit the particular material being treated without departing fromthe spirit and scope of the invention. I

The present invention may be used in treating'a'variety of sheetmaterials, as for example fabrics, papers and films; The compact andsimple nature of'the humidifying apparatus here described renders ithighly suitable for use on printing machines in treating papers or'films, as for example cellophane, which have become over-dry andbrittle during the ink-drying stages. Further, the novel method ofmaintaining the humidifying moisture under pressure only While thismoisture is contained between the sheet material being treated and thesurfaces of the heatedrolls results in a rapid and uniformhumidification of the sheet material and, in addition, reduces oreliminates any tendency for the humidifying atmosphere to be forced outfrom the enclosing chamber through the slots 31 and 33. I

It is seen from the above description that the objects of the inventionare well fulfilled by the method described. The description is intendedto be illustrative 4 only and it is to be understood that changes andvariations may be made without departing from the spirit and scope ofthe invention as defined by the appended claims.

I claim:

1. A method of humidifying a continuous traveling web of sheet materialincluding the steps of applying a humidifying liquid to one side of thetraveling web progressively in a longitudinal direction thereof,engaging successive portions of said one side of the traveling web withan endless heated surface to vaporize the liquid applied thereto,pressing transversely extending areas of said successive portions ofsaid web against the heated surface at longitudinally spaced areasthereof, urgingzthe longitudinal edges of said web extending betweensaid longitudinally spaced areas into snug contact'with the heatedsurface to thereby prevent the escape of the liquid as his vaporized andexpands whereby the vaporized liquid is caused to enter into thesuccessive portions or the web under a pressure greater than atmosphericpressure, and cooling the humidified web. v

2. A method of humidifying a continuous traveling web of'sheet materialincluding the steps of applying a humidi-' tying liquid to one side ofthe traveling webprogressively in a longitudinal direction thereof,engaging successive portions of said one side of the traveling web witha heated surface to vaporize the liquid applied thereto, pressingtransversely extending areas of said successive portions of said webagainst the heatedsurface at longi tudinallyspaced areas thereof, urgingthe longitudinal edges of said web extending-between said longitudinallyspaced areas into snug contact with the heated surface to therebyprevent the escape of the liquid'as it is vaporized and expands wherebythe vaporized liquid is caused to enter into the successive portions ofthe web under apressure greater than atmospheric pressure, and. coolingthe humidified web.

References (Zited in the file of this patent UNITED STATES PATENTS

1. A METHOD OF HUMIDIFYING A CONTINUOUS TRAVELING WEB OF SHEET MATERIALINCLUDING THE STEPS OF APPLYING A HUMIDIFYING LIQUID TO ONE SIDE OF THETRAVELING WEB PROGRESSIVELY IN A LONGITUDINAL DIRECTION THEREOF,ENGAGING SUCCESSIVE PORTIONS OF SAID ONE SIDE OF THE TRAVELING WEB WITHAN ENDLESS HEATED SURFACE TO VAPORIZE THE LIQUID APPLIED THERETO,PRESSING TRANSVERSELY EXTENDING AREAS OF SAID SUCCESSIVE PORTIONS OFSAID WEB AGAINST THE HEATED SURFACE AT LONGITUDINALLY SPACED AREASTHEREOF, URGING THE LONGITUDINAL EDGES OF SAID WEB EXTENDING BETWEENSAID LONGITUDINALLY SPACED AREAS INTO SNUG CONTACT WITH THE HEATEDSURFACE TO THEREBY PREVENT THE ESCAPE OF THE LIQUID AS IT IS VAPORIZEDAND EXPANDS WHEREBY THE VAPORIZED LIQUID IS CAUSED TO ENTER INTO THESUCCESSIVE PORTIONS OF THE WEB UNDER A PRESSURE GREATER THAN ATMOSPHERICPRESSURE, AND COOLING THE HUMIDIFIED WEB.